1. Field of the Invention
The present invention relates generally to building construction technologies. In particular, the present invention is directed to reinforcements for primary compression/tension members of high-rise concrete structures, such as columns and shear walls. The present invention also provides a method for the construction of high-rise concrete structures and elements of those structures.
2. Description of the Prior Art
As concrete structures become taller and slimmer, contractors face many new challenges in the construction field. Higher strength values are being required for concrete compression/tension members, requiring increased amounts of reinforcing steel. In multi-level concrete construction, it is a common construction practice to place vertical and horizontal steel reinforcement rods individually. It is also common practice in engineering and design that primary concrete members use steel grades of typically 60 ksi (Grade 60), and #11 (1.410″ nominal diameter) vertical longitudinal bars. That standard is based on the fact that an individual worker can be expected to pick up a single piece of the #11 rebar size, and be able to properly handle the weight of the bar. After the placement of the vertical bars, a worker would then place horizontal ties to attach the horizontal and vertical bars, as is standard practice. Once the grid or plurality of reinforcement rods is placed, a formwork or other means to contain the fluid form concrete having the desired dimensions is placed around the reinforcement. Concrete is then poured and vibrated as per standard practice to eliminate voids.
There are many externalities associated with the common standard practice of field placing standard steel reinforcements, including, but not limited to lack of quality of construction, very loose tolerances, consumption of large amounts of time for field work, use of valuable work space in field, lap splices, congestion of mass quantities of steel, problems associated with concrete placement with large quantities of steel, and field environment issues impacting workmanship.
As a result, the prior art has concentrated on the issues related to the placement of reinforcement steel for concrete structures. For example U.S. Pat. No. 5,392,580 to Baumann discloses a generally rectangular wire grid of welded construction that defines and maintains the position of rebar charged through the grid for the formation of structural column and girder cages. Pre-positioned ties are used to guide the rebar through the grid. The pre-positioned ties are then tightened such that the rebar is held firmly in place at the close tolerance positions defined by the prefabricated grid. As will be understood by those skilled in the art, the tightened ties prevent the spinning or rotation of the rebar. A plurality of such grids can be assembled into expandable bundles that may be expanded in an accordion-like fashion about the rebar, resulting in spaced grids for defining and maintaining the position of the rebar.
U.S. Pat. No. 5,359,829 to Voita discloses a method and apparatus for fabricating a drilled, concrete pier in the earth at a construction site. A template is provided, and vertical reinforcement bars are suspended from the template, generally defining the periphery of a reinforcement cage. Horizontal ties are then positioned at selected sides along the length of the reinforcement bars, and are fastened to the vertical reinforcement bars. Once concrete is poured to form the concrete pier, the template is removed from the ‘reinforcement cage.
Other modular cages involve continuous, spiral like, formed steel to act as the primary confining element and the aligning element.